Nowadays, people normally have a number of power-consuming devices, such as mobile phones, tablets, portable music devices, etc. These devices are usually battery-powered and need to be recharged after a certain period of use, e.g., every day or even multiple times each day. This undoubtedly imposes a burden on users of these types of devices because they must regularly check whether their devices need to be recharged. Furthermore, given that the devices may use different type of chargers, people may need to carry chargers and/or buy additional chargers in order to recharge their devices at different locations. If a person fails to recognize that power level of a device is low or that the devices has run out of power, he or she may not be able to use that device when it is needed.